Spark plug



Jan. 13, 1942.

G, M. PAULSON SPARK PLUG Filed Nov. '25, 1940 INVENTOR Patented Jan. 13, 1942 UNITED STATES PATENT OFFICE SPARK PLUG George M. Paulson, New York, N. Y.

Application November 23, 1940, Serial No. 366,803

6 Claims. -(Cl. 123-169) This invention relates to ceramic-insulated spark-plugs, that is to say spark-plugs in which part at least of the insulation is of ceramic material. In this specification, the term "ceramic material includes, without limitation, sintered metal oxide material.

Objects of the invention are to provide a ceramic-insulated spark-plug which is of simple construction; to provide a radio-shielded sparkplug wherein ceramic and cushioning insulations are combined to advantage; to provide a radioshielded spark-plugwherein ceramic and mica insulations are combined advantageously; to provide a ceramic and mica insulated, radio-shielded plug wherein possible flash-over paths are few and long, or the plug is short, or both; and otherwise to improve the construction of ceramic insulated spark-plugs, particularly radio-shielded plugs.

A further object of the invention is to provide a radio-shielded ceramic-insulated spark plug construction which is well adapted for the dissipation of heat, and in which the portion of a ceramic core body exposed to the hot gases may be of relatively small area.

In the spark-plug of this invention a downwardly tapered ceramic core body occupies the lower portion of a downwardly tapered opening in a metal body, the upper portion of which constitutes a radio-shielding barrel, and a tapered sleeve of mica or equivalent insulating material acts as a cushion between the coacting tapered seating surfaces of the ceramic and the metal bodies, and also serves as an insulating lining for the radio-shielding barrel.

Other objects, features and advantages of the invention will be apparent to those skilled in the art.

The drawing is a sectional view taken in a plane of the axis of a spark-plug embodying the invention.

Terms of orientation, such as upper and lower, when used hereinafter, refer to the drawing, not to a position of the spark-plug in use. The lower end of the spark-plug is the end that is inserted in the engine; the upper end is the outer end of the spark-plug.

In the illustrated embodiment of the invention the metal body of the spark-plug comprises a lower body or "shell 2, and an upper body 3, which screws into the lower body against a gasket 4, and provides a radio-shielding barrel and sck et for the external conductor (not shown). Customary means 6 is provided on the upper end connection (not shown) electrically connected with the shielding of the external conductor. The lower body 2 is externally threaded to screw into an opening of the engine cylinder and carries a ground electrode 1 of any suitable kind.

The metal body element 3 of the spark-plug of this invention has an opening 8 which tapers, i. e. progressively grows less in diameter, from top to bottom.

A ceramic core body 9 is correspondingly tapered on the outside, and is seated tightly in body element 3. To hold the ceramic core body down, against loosening or blowing out, an annular flange It) on the lower end of the metal body 3 is turned inward to coact with an annular recess I I in the outside of the lower portion of the core body. A soft metal gasket l2, preferably copper, is interposed between this flange and the surface of the annular recess, for gas-tightness.

The center electrode l3, which extends through the ceramic core body and projects below its lower end to cooperate with the ground electrode, may be held in the ceramic body in any of the known ways.

A laminated mica sleeve I5 is interposed between the coacting tapered seating surfaces of the metal and ceramic bodies 3 and 9, where it serves as a cushion, and extends upward above the ceramic body 9 to the upper end of the metal body 3, to serve as an insulating lining for the shielding barrel 5. A

The means In, for securing the ceramic core body, and the gas seal l2, are below the tapered seating surfaces of the members 3 and 9 and below the mica insulation I5. The lower portion of the ceramic body 9 projects downward into the cavity of the lower metal body 2 of the spark-plug,:but it is not necessary that the mica insulation be exposed to the engine cylinder gases.

changes may be made without departing from the invention.

I claim:

l. A spark-plug comprising a metal body having a downwardly tapered opening, a correspondingly tapered ceramic core body, said metal body extending above said ceramic body to constitute a radio-shielding barrel, and cushioning insulation interposed between the tapered seating surfaces of said bodies and extending upward as a of the metal barrel to engage with a suitable lining for said barrel.

2. A spark-plug comprising a metal body having a downwardly tapered opening, a correspondingly tapered ceramic core body, said metal body extending above said ceramic body to constitute a radio-shielding barrel, and laminated mica insulation lining said barrel and interposed as a cushion between the seating surfaces of said bodies.

3. A shielded spark-plug including a metal body having a tapered opening the lower portion of which serves as a seat for a ceramic core body and the upper portion of which serves as a shielding barrel to receive the end of an external conductor, a common tapered mica sleeve lining both the upper and lower portions of said opening, and a ceramic body held in the lower portion of the tapered opening and cushioned from contact with the metal wall of said opening by the mica sleeve.

lining for said barrel, and means below the seating region of said bodies for securing said ceramic body.

5. A radio-shielded spark-plug comprising a metal body having a downwardly tapered opening, a correspondingly tapered ceramic core body tightly seated in said metal body, said metal body extending above said ceramic core body to provide a radio-shielding barrel, insulation interposed as a cushion between said ceramic core body and said metal body and extending upward as a lining for said barrel, said ceramic body having a lateral recess, and securing means cooperating with said recess.

6. A radio-shielded spark-plug comprising a metal body having a downwardly tapered opening, a correspondingly tapered ceramic core body 4 tightly seated in said metal body, said metal body extending above said ceramic core body to provide a radio-shielding barrel, insulation interposed as a cushion between said ceramic core body and said metal body and extending upward as a lining for said barrel, said ceramic body having an annular groove, and an annular'securing' flange 'on said metal body turned into said recess.

GEORGE M. PAULSON. 

